Thank you for your post.
I have shown this to other Support Technicians, and no one has ever seen this before. I know that doesn't help you, but our consensus is that something is corrupt in your system, but we don't know what is causing it, which makes this more frustrating (for us and you)!
I did see that the Home.fp7 has an icon for FileMaker Pro 11. Did you ever install the trial version of FileMaker Pro 11 on this machine and then remove it? If you click once on Home.fp7, pull down the File menu and select "Get Info", are you able to change this open with FileMaker Pro 10? Are there any residual files with a FileMaker Pro 11 icon?
Any other information you can provide may be helpful in narrowing down this cause.